import lombok.experimental.ExtensionMethod; @ExtensionMethod({ExtensionMethodAutoboxing.Extensions.class}) class ExtensionMethodAutoboxing { public void test() { Long l1 = 1l; long l2 = 1l; Integer i1 = 1; int i2 = 1; String string = "test"; string.boxing(l1, i1); string.boxing(l1, i2); string.boxing(l2, i1); string.boxing(l2, i2); } static class Extensions { public static String boxing(String string, Long a, int b) { return string + " " + a + " " + b; } } }